iwlwifi: pcie: make FH debugfs file code easier to understand

The code seems fine, as buf won't be assigned when an error
is returned, but checking for the error first is easier to
understand.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
diff --git a/drivers/net/wireless/iwlwifi/pcie/trans.c b/drivers/net/wireless/iwlwifi/pcie/trans.c
index 7290f42..61ae1af 100644
--- a/drivers/net/wireless/iwlwifi/pcie/trans.c
+++ b/drivers/net/wireless/iwlwifi/pcie/trans.c
@@ -1434,16 +1434,15 @@
 {
 	struct iwl_trans *trans = file->private_data;
 	char *buf = NULL;
-	int pos = 0;
-	ssize_t ret = -EFAULT;
+	ssize_t ret;
 
-	ret = pos = iwl_dump_fh(trans, &buf);
-	if (buf) {
-		ret = simple_read_from_buffer(user_buf,
-					      count, ppos, buf, pos);
-		kfree(buf);
-	}
-
+	ret = iwl_dump_fh(trans, &buf);
+	if (ret < 0)
+		return ret;
+	if (!buf)
+		return -EINVAL;
+	ret = simple_read_from_buffer(user_buf, count, ppos, buf, ret);
+	kfree(buf);
 	return ret;
 }